They claim Sheeran copied the "heart" of the 1973 soul classic and repeated it continuously in 2014's Thinking Out Loud.

They allege that the British singer-songwriter continued to perform the song even after he was notified of the copyright infringement claim last year.

The family of Ed Townsend, who co-wrote Let's Get It On with Gaye, is demanding a jury trial and compensation for damages.

Thinking Out Loud reached number one in the UK and was a huge success in the US, where it won Song Of The Year at the Grammys.

The suit also names Thinking Out Loud co-writer Amy Wadge, as well as producer Jake Gosling, Sony/ATV Music Publishing, Atlantic Records and Warner Bros.

Sheeran's representatives did not immediately respond to a request for comment, b ut Wadge wrote on Twitter: "This is all I have ever done and the only thing I know how to do. The End!.. Keep calm and write songs."

Sheeran, who is taking a break from music, is already being sued for more than £13 million for allegedly copying a song released by X Factor winner Matt Cardle.